A “virtual machine” or a “VM” refers to a specific software-based implementation of a machine in a virtualization environment, in which the hardware resources of a real computer (e.g., CPU, memory, etc.) are virtualized or transformed into the underlying support for the fully functional virtual machine that can run its own operating system and applications on the underlying physical resources just like a real computer.
Virtualization works by inserting a thin layer of software directly on the computer hardware or on a host operating system. This layer of software contains a virtual machine monitor or “hypervisor” that allocates hardware resources dynamically and transparently. Multiple operating systems run concurrently on a single physical computer and share hardware resources with each other. By encapsulating an entire machine, including CPU, memory, operating system, and network devices, a virtual machine is completely compatible with most standard operating systems, applications and device drivers. Most modern implementations allow several operating systems and applications to safely run at the same time on a single computer, with each having access to the resources it needs when it needs them.
Virtualization allows one to run multiple virtual machines on a single physical machine, with each virtual machine sharing the resources of that one physical computer across multiple environments. Different virtual machines can run different operating systems and multiple applications on the same physical computer.
A node (e.g., server) hosting one or more virtual machines may utilize storage devices and storage management functionality that is external to the node. Typically this involves associating the one or more virtual machines at the node with an external networked storage environment having a set of storage controllers that communicate with a set of networked storage appliances via a network such as a Fiber Channel or Ethernet network. Thereafter, I/O requests (e.g., write requests or read requests) from the virtual machines at the node are provided to a storage controller at the external networked storage environment that fulfills the I/O requests and manages the data associated with I/O requests for the virtual machines.
In providing storage management functionality to the virtual machines, a dedicated storage controller at the external networked storage environment is assigned to all of the virtual machines at the node. All I/O requests pass through the dedicated storage controller before being fulfilled. Because all I/O requests from VMs in the node pass through single dedicated storage controller at the external networked storage environment, an excessive load may be incurred by the dedicated storage controller. Even where the dedicated storage controller is able to distribute a portion of its load to other storage controllers in the external networked storage environment, this is done so only after the dedicated storage controller has already received the I/O requests.